The invention relates to an improved pneumatic tire, especially as it pertains to traction, handling, wear and durability of a pneumatic tire.
A pneumatic tire provides cushioning between a vehicle and a driving surface, and a pneumatic tire and its construction have an influence on the handling properties of the vehicle. Since a pneumatic tire can be designed to optimize traction, the tire can have a strong influence on the acceleration of the vehicle. Other performance properties of the vehicle are also integrally related to the properties of the pneumatic tires which are mounted on the vehicle.
Tires are sometimes designed to have specific properties which are tuned to the kind of use that is to be made of a vehicle. For example, if a vehicle is used mainly for straight ahead driving, the pneumatic tire can be constructed to maximize the tread contact of the tire when the tire is going straight ahead. Similarly, when frequent cornering is expected, such as is encountered by race cars going counter-clockwise around oval tracks, the tires are sometimes constructed to stiffen the right sidewall to maximize the tread contact between the tire and the riding surface when the vehicle is cornering. Often, these specialized constructions sacrifice one property in exchange for maximizing another property.
When a tire is constructed to provide maximum tread contact with the riding surface for the kind of use most often encountered by the vehicle, the durability of the tire usually increases. When, for example, vehicle tires are especially constructed for race cars running on an oval track so that tread contact is maximized during cornering, it is expected that the number of tire changes during a race may be reduced.
When a vehicle is expected to encounter right-hand turns as well as left-hand turns, logic would indicate that the proper construction for such a tire would be the same or similar construction to that used on a vehicle that encounters a lot of straight ahead driving.
xe2x80x9cAspect ratioxe2x80x9d of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by 100% for expression as a percentage.
xe2x80x9cAxialxe2x80x9d and xe2x80x9caxiallyxe2x80x9d mean lines or directions that are parallel to the axis of rotation of the tire.
xe2x80x9cBeadxe2x80x9d means that part of the tire comprising an annular tensile member wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim.
xe2x80x9cBelt reinforcing structurexe2x80x9d means at least two layers of plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 17 degrees to 27 degrees with respect to the equatorial plane of the tire.
xe2x80x9cCircumferentialxe2x80x9d means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction.
xe2x80x9cEquatorial plane (EP)xe2x80x9d means the plane perpendicular to the tire""s axis of rotation and passing through the center of its tread.
xe2x80x9cFootprintxe2x80x9d means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under normal load and pressure.
xe2x80x9cInboard sidexe2x80x9d means the side of the tire nearest the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle.
xe2x80x9cOutboard sidexe2x80x9d means the side of the tire farthest away from the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle.
xe2x80x9cPlyxe2x80x9d means a continuous layer of rubber-coated parallel cords.
xe2x80x9cPneumatic tirexe2x80x9d means a laminated mechanical device of generally toroidal shape (usually an open torus) having beads and a tread and made of rubber, chemicals, fabric and steel or other materials. When mounted on the wheel of a motor vehicle, the tire, through its tread, provides traction and contains the fluid or gaseous matter, usually air, that sustains the vehicle load.
xe2x80x9cRadialxe2x80x9d and xe2x80x9cradiallyxe2x80x9d means directions radially toward or away from the axis of rotation of the tire.
xe2x80x9cSection heightxe2x80x9d (SH) means the radial distance from the nominal rim diameter to the outer diameter of the tire at its equatorial plane.
xe2x80x9cShoulderxe2x80x9d means the upper portion of a sidewall just below the tread edge.
xe2x80x9cSidewallxe2x80x9d means that portion of a tire between the tread and the bead.
xe2x80x9cTreadxe2x80x9d means a molded rubber component which, when bonded to a tire casing, includes that portion of the tire which comes into contact with the road when the tire is normally inflated and under normal load.
xe2x80x9cUnit tread pressurexe2x80x9d means the radial load borne per unit area (square centimeter or square inch) of the tread surface when that area is in the footprint of the normally inflated and normally loaded tire.
A pneumatic tire has at least a pair of parallel annular beads or bead-like structures in association with a carcass ply, belt or breaker reinforcement disposed over a crown area of the carcass ply, a tread disposed over the belts or breakers, and sidewalls disposed between the tread and the beads or bead-like structures. The tire of the invention has an asymmetric profile wherein the highest point in the tread is located between the centerline of the tread and the shoulder of the tread at 15% to 85% of the distance from the centerline to the shoulder of the tread.
In an illustrated tire, the highest point in the tread is 3 inches (7.62 cm) from the centerline (CL).
For various tire constructions embraced by the invention, the tread at its highest point may be 0.127 cm to 5 cm higher than the tread at a corresponding point on an opposed side of said centerline (CL).
In an illustrated tire, the highest point in the tread is 0.127 to 1.27 (cm) higher than a corresponding point in a tread half on the opposite side of the centerline (CL).
The pneumatic tire may be defined by an asymmetric profile wherein a peak (P) in the tread has a height and location defined by the formulae P=(sin Cxc2x7W)xe2x88x92(N/K) and L=xc2xdWxe2x88x92(0.3P/sin C), where
L is the distance of Peak shift from the centerline
P is the maximum differential in mold geometry from side to side
K is tire vertical spring rate
S is sidewall length
W is tread width
C is the average dynamic camber, and
N is the normal load
It is an object of the invention to provide a tire construction that provides good contact between the tread and the riding surface when a vehicle on which it is mounted is cornering, without sacrificing tread contact and handling properties when the vehicle is driven straight ahead.
Other objects of the invention will be apparent from the following description and claims.